Study of residual VNA measurement errors due to imperfect Thru-Reflect-Match calibration standards

We report results of our detailed study on vector-network-analyzer measurement errors after the TRM (Thru-Reflect-Match) calibration performed with imperfect SMA-connectorized standards at frequencies from 0.1 to 18 GHz. These residual errors are caused by an asymmetry of a thru/line standard and a load mismatch. To remove errors of the first type, we introduce a novel simple technique of the thru/line symmetrization, which utilizes an additional measurement of the same standard, but reversely connected to the VNA ports. To extract the load mismatch errors, we apply the multiline TRL (Thru-Reflect-Line) calibration as a reference one. To this end we use three common barrels of different lengths acting after their symmetrization as transmission line standards. With the VNA calibrated using the multiline TRL method, we characterize our mismatched load and then utilize its data to our modified TRM calibration. We show that this simple and low-cost approach results in improved accuracy of the TRM calibration. This aproach may be easily applied to enhance accuracy of the industrial VNA measurements on SMA devices.